Finely chop the onion with the garlic. Heat the oil and butter in a heavy pan, add the onion and garlic and cook over a medium heat for a few minutes until golden.

Drain and chop the tomatoes. Stir into the pan, season with salt and pepper and continue cooking for about 10 minutes until the sauce has thickened.

Top and tail the beans, then cook in boiling salted water for 6 minutes. Drain, cut in half and add to the tomato sauce. Mix well and continue cooking until the beans are tender, adding a little stock from time to time.

Add the chopped drained tuna and basil a few minutes before the end of the cooking time. Mix well and serve hot. Garnish with basil leaves if available.